Packagers, to ensure adequate sterilization, often fill bottles and containers with liquids or products at an elevated temperature of approximately 180° F. to 205° F. (82° C. to 96° C.) and seal with a closure before cooling. Manufacturers generally refer to this as a “hot-fill” container or as a “hot-filling” process. As the sealed container cools, a slight vacuum, or negative pressure, forms inside causing the container to slightly change shape, particularly, when made of polymer materials and generally having a somewhat flexible nature.
Typically, although not always, manufacturers produce these hot-fill containers in polyester materials, such as polyethylene terephthalate (PET), using a “stretch blow-molding” process, well known in the art, that substantially biaxially orients material molecular structure within the container. While PET materials are typical, other polymer materials, such as polypropylene, polyethylene, polycarbonate, and other polyesters, such as polyethylene naphthalate, are feasible using a variety of container production processes, also well known in the art, which may or may not establish the biaxial oriented material molecular structure.
Container and bottle designers attempting to control the change-in-shape from hot-fill often incorporate a plurality of generally recessed vacuum panels within a sidewall around the container's body. Those skilled in the art are well aware of a variety of vacuum panel configurations. The vacuum panels tend to focus the change-in-shape allowing the container to retain a pleasing generally uniform appearance. Retaining the pleasing generally uniform appearance is an important consideration to the packager and its customers. If the container should collapse in an un-uniform manner, the container appearance becomes less pleasing and the customer becomes reluctant to purchase, believing the product damaged.
Containers having a capacity between approximately one liter and three liters often feature a grip means to facilitate handling by the consumer, that is, to facilitate an easy confident grip of the container by thumb and forefingers of a hand. Accordingly, container and bottle designers often incorporate a grip surface typically within two diametrically apposed vacuum panels thereby allowing the vacuum panels to function together as a convenient grip or pinch-grip. Often the entire vacuum panel becomes the grip; however, the grip can also be a subsection of a substantially larger vacuum panel. Those skilled in the art are aware of a variety of grip-vacuum-panel configurations.
Packagers often place one or more spot labels on arcuate container surfaces between the grip-vacuum panels that often have a plurality of relatively shallow recessed ribs to increase rigidity, thus rendering these arcuate surfaces between the grip- or pinch-grip-vacuum panels unavailable to receive other generally recessed vacuum panels in addition to those used for the grip. Often containers having pinch-grip vacuum panels have only the two diametrically apposed vacuum panels, each with a grip surface, which must accommodate all vacuum related forces to the container while retaining the pleasing generally uniform appearance.
Containers having only two large diametrically apposed vacuum panels and the generally circular cross-sectional configuration are particularly vulnerable to unwanted changes-in-shape if the panels do not properly accommodate the vacuum related forces often causing the container to twist and assume a more oval cross-sectional or skewed oval cross-sectional configuration generally unpleasing to the consumer or customer.
Packagers attempting to reduce cost, require containers to have less material or to be lighter in weight. Said differently, the sidewall of the container has a thinner thickness and therefore is not as rigid. Accordingly, containers lighter in weight are particularly vulnerable to unwanted changes-in-shape, a particular problem for containers having the pinch-grip and otherwise a generally circular cross-sectional configuration featuring only two diametrically apposed vacuum panels with spot-labeling surfaces between. To function properly, the vacuum panels must be extremely flexible relative to other areas of the container.
However, while the panels accommodate vacuum related forces, the grip surfaces themselves must resist pinch-grip related forces from thumb and forefingers of the hand while the consumer pours contents from the container. Consequently, pinch-grip vacuum panels must be both ridged and flexible. Ridged to allow the customer or consumer to grip the container with ease and confidence, and flexible to accommodate vacuum related forces while retaining a uniform generally circular cross-sectional configuration without skewed oval cross-sectional appearance.
Accordingly, the inventor has discovered a new and novel pinch-grip vacuum panel combination providing controlled flexibility necessary to accommodate vacuum related forces thereby retaining the pleasing generally uniform appearance of the polymer container, while providing the rigidity necessary to function as a grip, thereby providing confidence to the consumer while handling the container.